Press your chocolate shards into the sides of the cake, letting the top shards extend a little ways past the top. They should be close to each other, but the occasional small space between chocolate curls is fine. Once the chocolate is applied, refrigerate the cake again to firm up the buttercream and chocolate.
Melt the remaining 8 oz of chocolate coating in the microwave. Use a pastry brush to brush the melted chocolate onto the sides of the cake. Cover every surface liberally, and don't be afraid to go back and add a second layer if it looks thin in spots. Once the sides are covered, pour a small amount of chocolate on top of the cake and spread it to the edges, so all of the buttercream is covered. Refrigerate the cake to set the chocolate completely.
Finally, brush some cocoa powder in random spots on the sides of the cake to give it the look of dusty tree bark. Your cake is finished! Store it in the refrigerator, but for the best taste and texture, allow it to come to room temperature before serving.